Spatial light modulators (SLMs) are devices or arrays of one or more devices that can control or modulate an incident beam of light in a spatial pattern that corresponds to an electrical input to the devices. The incident light beam can be modulated in intensity, phase, polarization or direction.
Some modulation can be accomplished through the use of Micro-Electromechanical System devices or MEMS that use electrical signals to move micromechanical structures to modulate light incident thereon. MEMS-based optical modulator devices generally require that pixels have flat optical surfaces that can be either tilted or displaced (vertical piston for example) in order to modulate light.